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Re: Shared_buffers hint

From: "Rafael Domiciano" <rafael(dot)domiciano(at)gmail(dot)com>
To: "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com>
Cc: "pgsql-admin(at)postgresql(dot)org" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Shared_buffers hint
Date: 2008-10-06 13:56:51
Message-ID: 3a0028490810060656o5d1482a0r1efdb594f3aeb16c@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-admin
I'm using 8.3.3 version in this machine..!So, the shared_buffers set to
100Mb is ok? Or 500Mb is better?
This server we call "Reporter Server", so it's used to do heavy reports for
a few users only (I could say 5 users).
What could be the best config for my server with:
2 Gb RAM
300 GB HD
Postgres 8.3
Dual Core

2008/10/6 Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>

> On Mon, Oct 6, 2008 at 5:52 AM, Rafael Domiciano
> <rafael(dot)domiciano(at)gmail(dot)com> wrote:
> > HI people,
> > I'm tuning a server that is a long time abandoned, and this server is a
> > little slow.
>
> What version pgsql is it running?  If it's 7.4 or before, you should
> look at upgrading it.  If you can't then a shared buffer setting in
> the 1000 to 10000 range is generally reasonable, but large
> shared_buffer settings (i.e. over 10000) are counterproductive for 7.4
> and before.
>
> > Now, in my postgresql.conf I have:
> > shared_buffers = 100Mb
>
> So it's a pretty modern version, since old ones can't read 100Mb as a
> setting.
>
> > mas_fsm_relations = 15000
> > mas_fsm_pages = 1600000
> > max_connections = 300
> > And I changin' to:
> > shared_buffers = 1000Mb
> >    (The server has 2 Gb of memory)
>
> 50% is kind of big.  Generally you either want it small enough that
> the OS can do the majority of the caching (it's usually better at
> caching large amounts of data) or large enough that the kernel cache
> doesn't come into play much.  50% means that everything is buffered
> exactly twice.
>
> > mas_fsm_relations = 15000
> >    (The Vacuum noticed me 608 relations)
> > mas_fsm_pages = 1600000
> >    (The Vacuum noticed me 500800 pages)
> > max_connections = 300
> >    (I did a "ps axf | grep postgres | wc -l" and the bash brings to me
> the
> > number of 120 and all the people is not online at now)
> > My qustion is about shared_buffers, in postgresql.conf I have: min 128kB
> or
> > max_connections*16kB  # (change requires restart)
> > So I did:
> > 300 * (16Kb / 1024) = 4,69?
> > What this result means?
>
> That's just the minimum the server needs to operate.  Not operate
> well, just operate.
>

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